Pillar[5]arene Stabilized Silver Nanoclusters: Immense Stability and Luminescence Enhancement Induced by Host-Guest Interactions.

Herein, we report the synthesis of a new class of functional silver nanoclusters (AgNCs) capped with pillar[5]arene (P5) based host ligands. These NCs are readily prepared via direct synthesis or ligand exchange synthesis and are stable at room temperature for over 4 months. The pillar[5]arene stabilized NCs (Ag29(LA-P5)12(TPP)2) endorse reversible host-guest interactions with neutral alkylamines and cationic quaternary ammonium guests. This results into the formation of spherical assemblies with unparalleled changes in their optical properties including an astonishing ≈2000-fold luminescence enhancement. This is the highest luminescence enhancement ratio reported so far for such atomically precise NCs. Our synthetic protocol paves the way for the preparation of a new generation of metal nanoclusters protected by macrocyclic ligands with molecular recognition and selectivity toward specific guests.